Quote:
Originally Posted by SuperTrooper
The best winter solution is to enclose the unit to keep the ambient temp as high as possible and keep wind away. Keeping it covered whenever not in use is a given for saving energy.
If you have access to natural gas or propane there are models out there and most companies make one. It's a special order item that I've never actually seen in a store, but I've seen a few in the field. They are supposed to be about 40% more efficient than electricity. Even better would be a unit connected to a heat pump. I have a heat pump for my inground pool and it uses about 20% of the electricity vs an electric heater. Higher initial cost, but it would pay for itself in 3-4 years and wouldn't break down as often. I've talked to my Hot Springs dealer and he said a custom unit without an electric heater would be about $1500 less. Since I already have the heat pump I'm already ahead.
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Electric heating using immersion elements is 100% efficient; its also more expensive (usually). You can get condensing gas heaters that advertise 98% efficiency, but the efficiency is dependent on the inlet water temp. At about 80°F, the condensing gas heaters are 98% efficient, but at 140°F, only about 84% efficient. At the typical hot tub temperature of 104°, my guess is that you would get about 92% efficiency. But the condensing gas heaters are expensive to buy. Natural gas and propane, at standard 82% efficiencies, would probably be cheaper for the life of the heater.
Softtub does something interesting; they noted that they could use the waste heat off the electric motor (that typically runs 24/7) and the friction of the water itself passing through the pump's impeller to heat the water. When the tub is covered, it heats it up nicely after a few days. They are probably the most energy efficient of the spas and hot tubs.
The typical use is to use the hot tub a lot when first bought, and then not so much after that. Sort of like exercise equipment. But maintenance goes on forever; you have to keep the water chlorinated and filtered or you create a health hazard.
